Q240401: BUG:Repeatedly Opening & Closing Recordset Increase Connections

Article: Q240401
Product(s): Microsoft Visual Basic for Windows
Version(s): WINDOWS:5.0,6.0
Operating System(s): 
Keyword(s): kbDatabase kbSQLServ kbGrpDSVBDB kbDSupport kbDAO360bug
Last Modified: 12-NOV-1999

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The information in this article applies to:

- Microsoft Visual Basic Enterprise Edition for Windows, versions 5.0, 6.0 
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SYMPTOMS
========

The number of connections opened on SQL Server increases indefinitely if a
Microsoft Data Access Objects (DAO) recordset is opened and closed repeatedly
when you use DAO version 3.6. This does not happen if you use DAO version 3.51.
You may see this behavior if you use sqlpassthrough in which the connection
string is specified in the OpenDatabase statement.

RESOLUTION
==========

Use a Querydef to create the connection instead of creating the connection in
the OpenDatabase statement.

STATUS
======

Microsoft has confirmed this to be a bug in the Microsoft products listed at the
beginning of this article.

MORE INFORMATION
================

Steps to Reproduce Behavior
---------------------------

1. Open a new Standard EXE project in Visual Basic. Form1 is created by default.

2. From the Project menu, choose References and then select Microsoft DAO 3.6
  Data Objects.

3. Place two command buttons, named Command1 and Command2, on the form, and then
  paste the following code in form code window:

  Dim db As Database
  Dim rs As Recordset
  Dim qd As QueryDef

  Private Sub Command1_Click()

  '-- Insert your own connect string here.
      Set db = OpenDatabase("", dbDriverNoPrompt, False, _
            "ODBC;DSN=sql7;UID=sa;PWD=;DATABASE=pubs;")
      Dim i As integer
      For i = 1 To 5
      '  reptq1 exists in the pubs database
          Set rs = db.OpenRecordset("reptq1", _
               dbOpenSnapshot, dbSQLPassThrough)
          rs.Close
      Next i
      
  End Sub

  Private Sub command2_Click()

     'Change the following string to match your path to the .mdb.
     Set db = OpenDatabase("d:\vbtest\db1.mdb")
     on error resume next
     db.QueryDefs.Delete "mysql7"
     on error goto 0
     Set qd = db.CreateQueryDef("mysql7")
     '-- Insert your own connect string below.
     With qd
       .Connect = "odbc;database=pubs;uid=sa;pwd=;dsn=sql7"
       .SQL = "select * from authors"
       .ReturnsRecords = True
     End With
     Dim i As Integer
     For i = 1 To 20
       Set rs = qd.OpenRecordset(dbOpenDynaset)
       rs.Close
     Next i
  End Sub

4. Open ISQL/W in SQL Server 6.5 or Query Analyzer in SQL Server 7.0 and run the
  sp_who stored procedure. Note the number of connections.

5. Run the form created in step 1 and click Command1. Note the number of
  connections by executing sp_who again. Repeat this process a few times and
  note that the number of connections continues to increase. If you get a
  connection failure you have probably reached your connection limit.

6. Next, click Command2 repeatedly and note the number of connections returned
  by sp_who.

REFERENCES
==========

For more information on SQLPassThrough Queries, see the following:

Haught, Dan; Jim Ferguson. Microsoft Jet Database Engine Programmer's Guide,
Microsoft Press, Second Edition, 1997, pages 397-401.

(c) Microsoft Corporation 1999, All Rights Reserved. Contributions by Margery
Simms, Microsoft Corporation.


Additional query words: jet Access 2000

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Keywords          : kbDatabase kbSQLServ kbGrpDSVBDB kbDSupport kbDAO360bug 
Technology        : kbVBSearch kbAudDeveloper kbZNotKeyword6 kbZNotKeyword2 kbVB500Search kbVB600Search kbVB500 kbVB600
Version           : WINDOWS:5.0,6.0
Issue type        : kbbug
Solution Type     : kbpending

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